Male jealousy tends to lurk beneath the surface, however. It surfaces in a very different way to female jealousy, which as we both know is often quite overt. I have never seen men get into "cat fights" like women do. IME men tend to be much more concerned about resource acquisition than women, and thus male jealousy will manifest in this domain (i.e. another man succeeding in/getting a job or career you yearned for).
And yeah, guys can become very envious about sex.